On Tue, Jan 06, 2015 at 12:15:25AM +0200, Pasi Kärkkäinen wrote:

On Tue, Dec 16, 2014 at 10:29:53PM +0200, Pasi Kärkkäinen wrote:

...

...

• xend is now disabled by default. You can enable it by running

chkconfig. xend has been removed from the tree entirely in Xen 4.5, so this should (hopefully) serve as a "wake-up-call" for people to begin the transition over to xend.

• A lot have things have changed -- please to test this so we can get

a good idea what may have broken.

I'll test soon. Thanks a lot!

Ok I just used a couple of hours testing Xen 4.4.1 rpms on CentOS 6.6 with Linux 3.10 dom0 kernel. This session was all about xm/xend testing. I manually enabled xend first.

What Works OK:

• Manually creating/managing guests with xm and domU cfgfiles in /etc/xen and LVM volumes as storage (phy backend).
• Manually creating/managing guests with xm and domU cfgfiles in /etc/xen and file images as storage (tap2:aio backend).
• Using virt-install to install PV domUs using LVM volumes as storage (phy backend).
• Using virt-manager to install PV domUs using LVM volumes as storage (phy backend).

What doesn't work:

• Using virt-manager to install PV domUs using file images as storage (tap:aio backend).

Oh, and obviously "virt-install" fails aswell when trying to use file images, same problem as with virt-manager.

Here's the virt-install commandline example you can use for testing:

virt-install -d -n blktaptest01 -r 2048 --vcpus=2 --disk /var/lib/libvirt/images/blktaptest01.img,size=8 --vnc -p -b virbr0 -l "http://ftp.funet.fi/pub/mirrors/centos.org/6.6/os/x86_64"

obviously you need to have a working libvirt-setup before running that command, and the libvirt/dnsmasq virbr0 bridge as created by libvirtd:

- yum install libvirt libvirt-daemon libvirt-daemon-network libvirt-driver-network libvirt-driver-xen virt-install virt-viewer virt-manager python-virtinst xorg-x11-xauth - service xend restart - service libvirtd restart

This libvirt/blktap2 file images failure with Xen 4.4 rpms is a regression from Xen 4.2 rpms, where blktap2 works OK with libvirt/virt-install/virt-manager.

The problem is most probably the fact that we had custom patches included in the xen4c6 libvirt rpms that we shipped with the Xen 4.2 rpms. We had to add two patches, one patch to fix the blktap2 backend type in libvirt, and one patch to fix the blktap2 backend type in virt-install or virt-manager, i'm not totally sure which one it was. Those patches should be included in the earlier libvirt source rpms, so we can check there. Or I can search thru my emails, because I hunted that down earlier aswell.

It seems we still need those patches with the latest libvirt rpms too.

The actual problem is libvirt/virt-manager tries to configure tap:aio: backend, which won't work. It needs to be tap2:aio.

I get the exactly same behaviour with xm/xend. "tap:aio" stalls and fails. "tap2:aio" works OK.

Ok so digging into the email archives it seems earlier we patched python-virtinst src.rpm, which seems to be the component used by both virt-install and virt-manager for new domain installations.

So we need to modify the virtinst/VirtualDisk.py file and change the:

DRIVER_TAP = "tap"

to

DRIVER_TAP = "tap2"

To change the default.

After that change the libvirt generated domain xml looks like this, from both virt-install and virt-manager and works OK:

<disk type='file' device='disk'> <driver name='tap2' type='aio'/> <source file='/var/lib/libvirt/images/blktaptest01.img'/> <target dev='xvda' bus='xen'/> </disk>

(virsh dumpxml <domain>)

-- Pasi

On Tue, Jan 06, 2015 at 01:55:57PM -0600, Johnny Hughes wrote:

...

Ok I just used a couple of hours testing Xen 4.4.1 rpms on CentOS 6.6 with Linux 3.10 dom0 kernel. This session was all about xm/xend testing. I manually enabled xend first.

What Works OK:

• Manually creating/managing guests with xm and domU cfgfiles in /etc/xen and LVM volumes as storage (phy backend).
• Manually creating/managing guests with xm and domU cfgfiles in /etc/xen and file images as storage (tap2:aio backend).
• Using virt-install to install PV domUs using LVM volumes as storage (phy backend).
• Using virt-manager to install PV domUs using LVM volumes as storage (phy backend).

What doesn't work:

• Using virt-manager to install PV domUs using file images as storage (tap:aio backend).

This libvirt/blktap2 file images failure with Xen 4.4 rpms is a regression from Xen 4.2 rpms, where blktap2 works OK with libvirt/virt-install/virt-manager.

The problem is most probably the fact that we had custom patches included in the xen4c6 libvirt rpms that we shipped with the Xen 4.2 rpms. We had to add two patches, one patch to fix the blktap2 backend type in libvirt, and one patch to fix the blktap2 backend type in virt-install or virt-manager, i'm not totally sure which one it was. Those patches should be included in the earlier libvirt source rpms, so we can check there. Or I can search thru my emails, because I hunted that down earlier aswell.

It seems we still need those patches with the latest libvirt rpms too.

The actual problem is libvirt/virt-manager tries to configure tap:aio: backend, which won't work. It needs to be tap2:aio.

I get the exactly same behaviour with xm/xend. "tap:aio" stalls and fails. "tap2:aio" works OK.

Now with the new python-virtinst and then new kernel from here:

http://people.centos.org/hughesjr/xen4-test/

But with the new libvirt-1.2 and xen 4.4 from this repo, everything seems to work with xend enabled.

Yep, with the updated python-virtinst all works now, also with the Xen 4.4 rpms.

Thanks a lot!

-- Pasi

On 01/06/2015 08:54 AM, Johnny Hughes wrote:

On 12/15/2014 12:24 PM, George Dunlap wrote:

...

At long last, I've got some beta CentOS 6 4.4.1 packages up on the CBS.

Major updates include:

• Update to Xen 4.4.1. Also includes all XSAs through 114
• Update to latest blktap 2.5
• Updated libvirt packages (1.2.10), which work well with libxl

To use, add the following to a file in /etc/yum.repos.d:

[virt-testing] name=CentOS-$releasever - virt-testing baseurl=http://cbs.centos.org/repos/virt6-testing/$basearch/os/ gpgcheck=0 enabled=1

Notes:

• git repo with all the changes to xen can be found here:

https://github.com/gwd/sig-virt-xen out/virt6/update-4.4.1-4

• The signing infrastructure is not in place, so the binaries are not signed.

• xend is now disabled by default. You can enable it by running

chkconfig. xend has been removed from the tree entirely in Xen 4.5, so this should (hopefully) serve as a "wake-up-call" for people to begin the transition over to xend.

• A lot have things have changed -- please to test this so we can get

a good idea what may have broken.

-George

George,

I don't mind if xend is on or off, but the virt-manager (virt-install, etc.) that is included with the current xen4 tree will not work at all with libxl.

We therefore do not have a GUI front end that can do libxl at this time.

I might suggest leaving xend on for 4.4.x and we stabilize on 4.4.x on the production branch, and then start a testing branch that will be 4.5 (or newer) with a newer libvirt, virt-manager, qemu, etc.

I thought maybe a new kernel as well, but based on this:

https://www.kernel.org/category/releases.html

It seems 3.10.x (at Sept 2016) is the best LTS kernel for support purposes.

So, I can't read :) .. 3.10.x stops in Sept 2016

Looks like jumping to 3.14.x would be required at some point, might as well try to do that in the testing branch as well.

Thanks, JOhnny Hughes

On Tue, Jan 6, 2015 at 2:54 PM, Johnny Hughes johnny@centos.org wrote:

George,

I don't mind if xend is on or off, but the virt-manager (virt-install, etc.) that is included with the current xen4 tree will not work at all with libxl.

We therefore do not have a GUI front end that can do libxl at this time.

I might suggest leaving xend on for 4.4.x and we stabilize on 4.4.x on the production branch, and then start a testing branch that will be 4.5 (or newer) with a newer libvirt, virt-manager, qemu, etc.

Are you sure? I thought I remembered trying virt-install with libvirt and having success. Pasik, did you try this?

If virt-manager really doesn't work with libxl, then yes, we should probably sort that out one way or another.

I'd really like to be able to leave xend off, to make sure people are starting to think about migration; but if there's no way to get virt-manager to work without it, we'll just have to turn xend back on and see what we can do.

I thought maybe a new kernel as well, but based on this:

Yes, updating to a new kernel (probably 3.14) is my next big work item.

-George